Best pals Gigi Hadid and Taylor Swift have made a wedding pact, insiders say, vowing they will play key roles in planning each other's walk down the aisle, RadarOnline.com can reveal.

Sources said it's not a matter of if, but when the deal is sealed for Hadid, 30, and 35-year-old songbird Swift with their future grooms. Article continues below advertisement

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"They've made a pledge to be a huge part of each other's wedding planning when the time comes, and they're looking forward to a huge bachelorette bash to celebrate the happy news once it's all official," said an insider.

Hadid and A Star Is Born hunk Bradley Cooper , 50, are careening toward an engagement, and insiders sa

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